1. Field of the Invention
The present invention is directed to alkylamino oxamides that are derived from the condensation of primary N,N-(dialkylaminoalkyl)amines (or mixtures of primary N,N-(dialkylaminoalkyl)amines) with oxalate esters (or oxalic acid). There is thus provided a class of catalysts containing active hydrogen groups that have unique utility as low odor, non-fugitive catalysts for the preparation of polyurethanes. The use of these catalysts permits the preparation of urethane foams having improved physical properties relative to those obtained using conventional amine catalysts.
2. Description of Related Art
Polyurethane foams are produced by allowing a polyisocyanate to react with a compound containing two or more active hydrogen groups. The active hydrogen-containing compounds are typically polyether or polyester polyols, primary and/or secondary polyetheramines, and water. Two major reactions occur between these reactants during the preparation of polyurethane foam. These reactions must proceed simultaneously and at a competitively balanced rate during the process in order to yield polyurethane foam with desired physical characteristics.
Reaction between the isocyanate and the polyol or polyamine, usually referred to as the gel reaction, leads to the formation of a polymer of high molecular weight. This reaction is predominant in solid polyurethane elastomers and in foams blown exclusively with low boiling point organic compounds such as methylene chloride or pentane. This reaction increases the viscosity of the mixture and generally contributes to crosslink formation when polyfunctional polyols, polyamines or polyisocyanates are used.
The second major reaction occurs between the isocyanate and water. This reaction also adds to urethane polymer growth, and is important for producing carbon dioxide gas, which promotes foaming. As a result, this reaction often is referred to as the blow reaction. Both blow and gel reactions occur in foams blown partially or totally with carbon dioxide gas. In fact, the in situ generation of carbon dioxide by the blow reaction plays an essential part in the preparation of xe2x80x9cone-shotxe2x80x9d, water blown polyurethane foams. Water-blown polyurethane foams, particularly flexible foams, are produced using either molded or slabstock foam processes.
In order to obtain good urethane foam structure and properties, the gel and blow reactions must proceed simultaneously and at optimum balanced rates. For example, if the carbon dioxide evolution is too rapid in comparison with the gel reaction, the foam tends to collapse. Alternatively, if the gel reaction is too rapid in comparison with the blow reaction generating carbon dioxide, foam rise will be restricted, thus resulting in a high-density foam. Also, poorly balanced crosslinking (gel) reactions will have an adverse effect on foam stability. In practice, the balancing of these two reactions is controlled by the nature of the catalysts used in the process.
Typically, the catalysts used for making polyurethanes are of two general types: tertiary amines (mono and poly) and organo-tin compounds. Organometallic tin catalysts predominantly favor the gelling reaction, while amine catalysts exhibit a more varied range of blow/gel balance. Using tin catalysts in flexible foam formulations also increases the quantity of closed cells contributing to foam tightness. Tertiary amines can be effective as catalysts for both the blow and the chain extension reactions and are often used in combination with the organic tin catalysts. Typical tertiary amine catalysts include bis-(dimethylaminoethyl)ether and triethylenediamine, among others, and typical organometallic compounds are stannous octoate and dibutyltindilaurate.
Most tertiary amines (including those noted above) used for the catalysis of polyurethane foam forming reactions are of the fugitive type. Fugitive amines are so designated because they are not bound to the urethane polymer matrix and, therefore, can leave the matrix under certain conditions. This fugitivity results in the emission of fumes from hot foam in both molded and slabstock foam processes. Airborne amine vapors can be an industrial hygiene problem in foam production plants. A particular effect of the amine vapor is glaucopsia, also known as blue-haze or halovision. It is a temporary disturbance of the clarity of vision. Fugitive amines can also cause problems, such as the fogging of automotive windshields, when they are used in the preparation of fully fabricated interior automotive parts. Many prior art fugitive amines also impart an unacceptably strong amine odor to the polyurethane foam. Because of these issues, there is increasing demand in the industry for low fugitivity, low odor catalysts.
Many approaches have been taken to define amine catalysts with reduced fugitivity. Some examples are given below.
Various active hydrogen containing polyurethane catalysts are described in the article: xe2x80x9cFactors Affecting the Discoloration of Vinyl That Has Been Molded Against Urethane Foamxe2x80x9d, R. L. Zimmerman and T. L. Austin, Polyurethane World Congress, Sep. 29-Oct. 2, 1997, pp. 693-697, 1987.
U.S. Pat. No. 3,073,787 discloses the use of various propionamide derivatives as polyurethane catalysts.
U.S. Pat. No. 3,234,153 discloses the use of various acetamides as catalysts for the preparation of polyurethanes.
U.S. Pat. No. 3,243,389 discloses a variety of aminourethane and/or aminourea catalysts for the preparation of polyurethane plastics.
U.S. Pat. No. 3,784,599 discloses the use of water-soluble quaternary ammonium phthalocyanine dyestuffs useful in the dyeing art.
U.S. Pat. No. No. 4,007,140 discloses a tertiary amine having the general formula: 
wherein X is the residue of an organic acid X(OH)n, n being the number of acidic groups present in the acid. The amines are said to be useful as low odor catalysts in the production of polyurethanes.
U.S. Pat. No. 4,049,591 discloses compounds of the formula 
where n is 2, Rxe2x80x3 is lower alkyl, R is hydrogen or lower alkyl and Y is selected from the group consisting of CN, CONH2, CO2Rxe2x80x2, CONR2 and CORxe2x80x2 where Rxe2x80x2 independently is hydrogen, lower alkyl or aryl. A method of producing a polyurethane by utilizing said above compounds as catalysts in reacting an organic polyisocyanate with an organic polyester polyol or polyether polyol in the presence of said catalyst is also disclosed.
U.S. Pat. No. 4,194,069 discloses N-(3-dimethylaminopropyl)-Nxe2x80x2-(3-morpholinopropyl)urea and a method of producing a polyurethane by utilizing this compound as a catalyst in reacting an organic polyisocyanate with an organic polyester polyol or polyether polyol in the presence of said catalyst.
U.S. Pat. No. 4,348,536 discloses compounds and the use thereof in producing polyurethane resins. The compounds correspond to the following formula: 
wherein n is an integer of from 1 to 5, R is a C1-C5 alkyl group, Y is a C1-C5 alkyl group or a 
and Z is a 
where n=0 or 1, X is xe2x80x94Oxe2x80x94 or 
and Rxe2x80x2 is an aliphatic group having from 1 to 15 carbon atoms and may contain ester, ether, or amide groups or tertiary nitrogen and, when m=0, Rxe2x80x2 may be a hydrogen atom.
U.S. Pat. No. 4,644,017 discloses composite polyisocyanate addition products formed from (1) the reaction product of a compound having at least two isocyanate-reactive hydrogen atoms and a molecular weight of from 400 to 10,000, a polyisocyanate and a catalyst which is a diffusion stable amino alkyl urea having tertiary amino groups and corresponds to the formula 
in which R1, R2, R3, R4, R5, R6, R7 and n each represent specified groups or values and (2) another different material such as polyvinyl chloride, ABS, lacquers and textiles.
U.S. Pat. No. 5,489,618 discloses a process for preparing a polyurethane foam according to the one-shot foaming process by reactions between a polyisocyanate and an active hydrogen-containing component including water and an organic polyol wherein said reactions are conducted in the presence of a salt of a tertiary amine and a carboxylic acid having hydroxyl functionality.
U.S. Pat. No. 5,824,711 discloses a method for preparing a polyurethane foam which comprises reacting an organic polyisocyanate and a polyol in the presence of a blowing agent, a cell stabilizer and a catalyst composition that is an N,N,Nxe2x80x2-trimethylbis(aminoethyl)ether substituted urea.
U.S. Pat. No. 6,077,877 discloses amine/amide catalysts for use in catalyzing the formation of polyurethane. The amine/amide catalysts, which have low fugitivity due to their reactivity with isocyanates, and good catalytic activity, have the structure 
wherein Q is CzH2z+1, or (CH2)nN(R3)kT, T is a monovalent C1-C4 alkyl, amino-C1-C4-alkyl, mono-C1-C4 -alkylamino-C1-C4-alkyl, or di-C1-C4-alkylamino-C1-C4-alkyl group, or T is a divalent alkyl, amine substituted alkyl, alkylaminoalkyl, or alkoxyalkyl group which forms with the nitrogen atom shown in structure (I) to which T is attached a cyclic structure which incorporates up to 6 carbon atoms in the ring as well as the nitrogen atom shown in structure (I), which cyclic structure may be substituted with C1 to C4 alkyl; k=0 or 1, being 1 if T is a monovalent group and 0 if T is a divalent group; R2=H or CzH2z+1; R3=CzH2z+1; R4=H; R5=H or CH3; n=2 to 6; and z=1 to 4. Each R3 and T may be the same or different, as may each value of n and z. One specific preferred range of structures is those in which Q is CzH2z+1.
DE 3,027,796 discloses a variety of dialkylaminoalkyl urea catalysts for preparation of polyurethane foams.
It is clear from the above that significant effort has been focused on the use of amine containing urea and amide derivatives as low fugitivity, low odor catalysts.
The present invention is directed to the use of a class of compounds that are known in the art (EP 575836, EP 327379, U.S. Pat. No. 3,543,306, CH 483461), but that have not been used as catalysts in the preparation of polyurethanes.
The present invention relates to a process for making polyurethanes (all types) using a class of low odor, non-fugitive amine catalysts heretofore not used in the preparation of such polyurethanes. The useful catalyst compounds are alkylamino oxamides of the general structure: 
wherein:
R1 and R2 are independently selected alkyl groups or can be taken together to form a five or six-membered heterocyclic ring;
R3 and R4 are independently selected from the group consisting of hydrogen and alkyl;
n is 2 or 3;
x is 0 or 1;
Y is selected from the group consisting of O and NR9,
xe2x80x83wherein:
R9 is selected from the group consisting of hydrogen and alkyl; and
X is selected from the group consisting of OR10 and G,
xe2x80x83wherein:
R10 is selected from the group consisting of hydrogen and alkyl; and
G is 
xe2x80x83wherein:
R5 and R6 are independently selected alkyl groups or can be taken together to form a five or six-membered heterocyclic ring;
R7 and R8 are independently selected from the group consisting of hydrogen and alkyl;
n is 2 or 3;
x is 0 or 1; and
Yxe2x80x2 is selected from the group consisting of O and NR11,
wherein R11 is selected from the group consisting of hydrogen and alkyl.
Thus, where X is G, the general structure of the alkylamino oxamides used in the process of the present invention can be considered to be GCOCOGxe2x80x2 wherein G and Gxe2x80x2 are the same if a single primary N,N-(dialkylaminoalkyl)amine is used and are different if a mixture of N,N-(dialkylaminoalkyl)amines is used.
The terminal tertiary nitrogens can also be part of ring structures, such as morpholines or imidazoles.
Admixtures of these alkylamino oxamides with at least one hydroxy carboxylic acid, such as salicylic acid, gluconic acid, dimethylol propionic acid, chloro-acetic acid, and the like can also be advantageously employed in the practice of the present invention.
More particularly, the present invention is directed to a process for the synthesis of polyurethanes comprising reacting polyurethane-forming reactants in the presence of an effective amount of a catalyst comprising at least one alkylamino oxamide of the structure: 
wherein:
R1 and R2 are independently selected alkyl groups or can be taken together to form a five or six-membered heterocyclic ring;
R3 and R4 are independently selected from the group consisting of hydrogen and alkyl;
n is 2 or 3;
x is 0 or 1;
Y is selected from the group consisting of O and NR9,
xe2x80x83wherein:
R9 is selected from the group consisting of hydrogen and alkyl; and
X is selected from the group consisting of OR10 and G,
xe2x80x83wherein:
R10 is selected from the group consisting of hydrogen and alkyl; and
G is 
xe2x80x83wherein:
R5 and R6 are independently selected alkyl groups or can be taken together to form a five or six-membered heterocyclic ring;
R7 and R8 are independently selected from the group consisting of hydrogen and alkyl;
n is 2 or 3;
x is 0 or 1; and
Yxe2x80x2 is selected from the group consisting of O and NR11,
wherein R11, is selected from the group consisting of hydrogen and alkyl.
As stated above the compounds employed in the practice of the present invention are broadly defined as alkylamino oxamides having the general structure: 
wherein:
R1 and R2 are independently selected alkyl groups or can be taken together to form a five or six-membered heterocyclic ring;
R3 and R4 are independently selected from the group consisting of hydrogen and alkyl;
n is 2 or 3;
x is 0 or 1;
Y is selected from the group consisting of O and NR9,
xe2x80x83wherein:
R9 is selected from the group consisting of hydrogen and alkyl; and
X is selected from the group consisting of OR10 and G,
xe2x80x83wherein:
R10 is selected from the group consisting of hydrogen and alkyl; and
G is 
xe2x80x83wherein:
R5 and R6 are independently selected alkyl groups or can be taken together to form a five or six-membered heterocyclic ring;
R7 and R8 are independently selected from the group consisting of hydrogen and alkyl;
n is 2 or 3;
x is 0 or 1; and
Yxe2x80x2 is selected from the group consisting of O and NR11,
wherein R11, is selected from the group consisting of hydrogen and alkyl.
In the above structural formulae, R1, R2, R5, and R6 can be the same or different and, in one embodiment, are alkyl, preferably lower alkyl of from one to four carbon atoms, such as, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl. Alternatively, R1 and R2 can be taken together to form a heterocyclic ring of five or six members, such as pyrroles, pyrrolines, pyrrolidines, pyrazoles, imidazoles, triazoles, dioxazoles, oxathiazoles, piperazines, isoxazines, morpholines, and the like. Imidazoles and morpholines are preferred. Similarly, where R5 and R6 are present, they can also be taken together to form a heterocyclic ring of five or six members, which can be of the kind described above and which can be the same as, or different from, a ring formed from R1 and R2.
Where R1 and R2 are alkyl, it is preferred that they be the same. It is also preferred that when R5 and R6 are present and are alkyl they be the same. It is most preferred that when R1, R2, R5, and R6 are all present, they all be the same, whether they be alkyl or heterocyclic rings.
R3, R4, R7, and R8 in the above structural formulae are independently selected from the group consisting of hydrogen and alkyl. When any of R3, R4, R7, or R8 is alkyl, it is preferred that it be lower alkyl of from one to four carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl. It is preferred that R3 and R4, R7, and R8, when present, be the same and that they be hydrogen or methyl.
Y is oxygen or NR9 where R9 is hydrogen or alkyl. Where R9 is alkyl, it is preferably lower alkyl of from one to four carbon atoms as described above. Yxe2x80x2 can be the same or different from Y and similarly is oxygen or NR11 where R11 is hydrogen or alkyl. Where R11 is alkyl, it is preferably lower alkyl of from one to four carbon atoms as described above.
X can be either OR10 or G, where R10 can be hydrogen or alkyl. Where R10 is alkyl, it is preferably lower alkyl of from one to four carbon atoms as described above. It is preferred that X be G.
The alkylamino oxamides employed in the practice of the present invention are derived from the condensation of primary N,N-(dialkylaminoalkyl)amines (or mixtures of primary N,N-(dialkylaminoalkyl)amines) with oxalate esters (or oxalic acid). There is thus provided a class of catalysts containing active hydrogen groups that have unique utility as low odor, non-fugitive catalysts for the preparation of polyurethanes. The use of these catalysts permits the preparation of urethane foams having improved physical properties relative to those obtained using conventional amine catalysts.
These alkylamino oxamides, themselves, while not new compositions, have not previously been employed as polyurethane catalysts. They have low odor and are non-fugitive in typical foams. While not wishing to be held to any theory of mechanism, the inventors believe that the alkylamino oxamides are non-fugitive because they have the potential to react with isocyanates (through the oxamide Nxe2x80x94H group) and/or because they have relatively high molecular weight and polarity.
In addition, the inventors have found that mixtures of these alkylamino oxamides with one or more hydroxy carboxylic acids are also good catalysts, producing urethane foams with unexpectedly good physical properties. Hydroxy acids that can be employed in combination with the alkylamino oxamides in the practice of the present invention include, but are not limited to, salicylic acid, gluconic acid, dimethylol propionic acid, chloroacetic acid, m-hydroxybenzoic acid, p-hydroxybenzoic acid, gallic acid, syringic acid, tartaric acid, citric acid, 2-hydroxymethylpropionic acid, dihydroxybenzoic acid, glycolic acid, beta.-hydroxybutyric acid, cresotic acid, 3-hydroxy-2-naphthoic acid, lactic acid, malic acid, resorcylic acid, hydroferulic acid and the like. Salicylic acid is preferred. Lactones (cyclic esters) wherein a hydroxyl group and a carboxyl group on the same molecule of the above formula react with one another to form a hydroxy acid suitable for practicing the present invention also can be used. Such lactones include gamma-butyrolactone. Hydroxy acids useful in the practice of the present invention generally have molecular weights below about 250.
Thus the alkylamino oxamides employed in the practice of the present invention are unique as catalysts for polyurethanes in at least three different ways:
1. U.S. Pat. No. 4,348,536 cites earlier patents that suggest that polyurethane catalysts containing active hydrogen groups are not effective because they are xe2x80x9cgradually built into the polymer structurexe2x80x9d and consequently are no longer available to help finish the cure of the polymer (especially polyurethane foams). The compounds of the present invention are alkylamino oxamides in which the amide groups are secondary, not tertiary, derivatives, i.e., they contain active hydrogen groups. The reactivity studies provided in the Examples below confirm that it is always possible to define a use level of alkylamino oxamide that will give a reactivity profile reasonably close to that of a given control catalyst.
2. It has also been found that the catalysts that result from mixing these alkylamino oxamides with hydroxy carboxylic acids are particularly effective products. They provide polyurethane foams with good cure characteristics (long exit time, same de-mold time) and unexpectedly improved physical properties when compared to those prepared with conventional amine catalysts.
3. These new polyurethane catalysts are non-fugitive.
The alkylamino oxamides can catalyze the reaction between an isocyanate functionality and an active hydrogen-containing compound, i.e. an alcohol, a polyol, an amine or water with isocyanate to make polyurethanes and the blowing reaction of water with isocyanate to release carbon dioxide for making foamed polyurethanes.
The polyurethane products are prepared using any suitable organic polyisocyanates well known in the art including, for example, hexamethylene diisocyanate, phenylene diisocyanate, toluene diisocyanate (xe2x80x9cTDIxe2x80x9d) and 4,4xe2x80x2-diphenylmethane diisocyanate (xe2x80x9cMDIxe2x80x9d). Especially suitable are the 2,4- and 2,6-TDI""s individually or together as their commercially available mixtures. Other suitable isocyanates are mixtures of diisocyanates known commercially as xe2x80x9ccrude MDIxe2x80x9d, also known as PAPI, which contain about 60% of 4,4xe2x80x2-diphenylmethane diisocyanate along with other isomeric and analogous higher polyisocyanates. Also suitable are xe2x80x9cprepolymersxe2x80x9d of these polyisocyanates comprising a partially prereacted mixture of a polyisocyanate and a polyether or polyester polyol.
The catalysts of the present invention can be used in mixtures with other catalysts, surfactants, or other additives or polyurethane components as are known in the art.
Foam formulations with which the alkylamino oxamides can be used as catalysts usually comprise (a) a polyether polyol containing an average of more than two hydroxyl groups per molecule; (b) an organic polyisocyanate; (c) at least one catalyst for production of polyurethane foam; (d) water; (e) a surfactant, preferably any of the silicone/polyether copolymers known in this field for this purpose; and (f) an inert gas.
The polyols have an average number of hydroxyl groups per molecule of at least slightly above 2 and typically 2.1 to 3.5. Generally, the polyol should have an equivalent weight of about 400 to 1500 or even 400 to 3000 grams/equivalent and an ethylene oxide content of less than 20%. Useful polyols include, but are not limited to, polyether polyols such as alkylene oxide adducts of polyhydroxyalkanes, alkylene oxide adducts of non-reducing sugars and sugar derivatives, alkylene oxide adducts of polyphenols, and alkylene oxide adducts of polyamines and polyhydroxyamines . The alkylene oxides are preferably based on ethylene oxide or propylene oxide.
The water generally comprises on the order of 1 to 12 php (parts by weight per hundred parts of polyol).
Other additives may be added to the polyurethane foam to impart specific properties to the foam, including, but not limited to, coloring agents, flame retardants, and GEOLITE(copyright) Modifier foam additives (available from Organo Silicones Group of Crompton Corporation). The inert gas is one which is soluble in the foam formulation at elevated pressures, but will come out of solution (i.e., blow) at atmospheric pressure. An exemplary such gas is CO2, but nitrogen, air, or other common gases, including hydrocarbon gases, such as methane and ethane may also be used. The inert gas may also comprise a volatile organic compound such as a pentane isomer or a hydrochlorocarbon that boils above ambient temperature, but has a sufficiently high vapor pressure at ambient temperature that its vapor represents a substantial component of the gas in the cells of the foam.
The silicone copolymer surfactants should be capable of helping to form a stable foam and should be present in an amount effective to stabilize the polyurethane foam, i.e., an amount which is generally about 0.05 to 5 wt. percent of the total reaction mixture, preferably 0.2 to 1.5 wt. percent.
The foam is manufactured by mixing the ingredients together such that byproduct gas generated during the reaction foams the polyurethane. The foam can also be made by the injection of inert gas, whereby the reactants are put under high pressure (i.e., at least greater than atmospheric pressures) so that the inert gas is dissolved in the reactant mixture. Then the mixture is flashed, by releasing the pressure, which causes the gas to form bubbles at nucleation sites in the foaming system and thus act as a blowing agent. This produces a reduced density foam. For a more complete description of this process and the equipment required therein, see European Patent Publication No. 0 645 226 A2, which is incorporated herein by reference.
The compounds of the present invention may also be used as catalysts in non-foam polyurethane reactions, such as polyurethane elastomer formation. In such polyurethanes, the water in the formulation is often replaced with a chain extender, which is a low molecular weight ( less than 400) active hydrogen containing compound with at least two reactive groups. Examples are 1,4-butanediol, ethylene glycol, diethylene glycol and ethylene diamine.
The conditions and formulations for these reactions are known in the art, e.g., xe2x80x9cPolyurethane Handbook,xe2x80x9d 2nd ed., Gunter Ortel, ed., Hanser Publishers, Cincinnati, 1994, which is incorporated herein by reference.